This has been floating around the Internet for years so it’s nothing new but for anyone that puts a premium on battery life on their Surface Pro (original or Pro 2) like I do (I specifically need to extend the battery because 90% of what I do with it is take handwritten notes using the stylus & OneNote) then this might interest you.

Adjusting Max Processor State in Windows 8 In order to extend the battery life a bit, all you have to do is change the the maximum processing power percentage assigned to the Power Options profile on your device from 100% to 80%. This provides a noticeable difference in battery life – some have reported up to 1-2 hours, & for most purposes like inking in OneNote or browsing, you’ll probably won’t see any change in performance.

To accomplish this:

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Makes sense and it's easy enough to tweak too. Going to have to give this a try on my Pro...